1. Field of the Invention
The present invention relates to a device and a method for lane keeping assistance for a motor vehicle.
2. Description of the Related Art
Lane keeping assistance systems having automatic intervention in the vehicle dynamics or automatic lane correction are also designated as intervening lane keeping assistance systems, LDP (lane departure prevention), LKS (lane keeping system) or LKAS (lane keeping assistant system).
The lane keeping assistance systems detect the vehicle's driving environment using a driving environment sensor system, and intervene in the vehicle dynamics so as to prevent the vehicle from leaving the lane. In this case, different actuators of the vehicle may be activated, particularly the vehicle's steering and/or braking. Automatic interventions in vehicle steering are possible particularly in the case of electromechanical steering (EPS, electric power steering), active steering (AFS, active front steering) or RWS (rear wheel steering). Braking interventions may take place particularly by one-sided braking interventions or asymmetrical braking interventions. Because of the interventions in the vehicle's actuator system, a yaw torque is impressed about the vertical axis, which induces the vehicle to a yawing motion to prevent it from leaving the lane.
In this instance, LKS systems are known which are based on a continuous control variable, particularly the steering torque, and are active over the entire roadway width. Such regulations may be sensed as being unpleasant, since the control variable intervenes continuously and independently of the driver's intention. Other driver assistance systems are designed to undertake the intervention as a function of the exceeding of a control threshold. In such systems it is, however, disadvantageous that the control threshold typically acts independently of the position of the vehicle with respect to the roadway boundary, and with that, in the case of wide roadways, frequently intervenes too early.
Published German patent application document DE 10 2008 040 627 A1 describes a device and a method for operating a steering assistance system having adaptation in case of the approach of a driving environment object. In this instance, an intervention-free area at the edge of one's own lane is defined, outside of which no driving dynamics interventions of the lane keeping assistance system takes place.